4tablespoons(57g)salted butter, softened or even melted and cooled
¼cup(53g)lightly packed brown sugar
½cup(106g)granulated sugar
½cup(113g)sour cream
1largeegg
1teaspoonvanilla extract
⅔ - 1cupmashed ripe bananas, (about 2 large bananas)
1cup(142g)all-purpose flour
½teaspoonbaking soda
¼teaspoonsalt
Browned Butter Frosting:
4tablespoons(57g)butter
2cups(228g)powdered sugar
½teaspoonvanilla extract
1-2tablespoonsmilk or cream (see note)
Instructions
Preheat the oven to 350 degrees F. Lightly grease a 9X13-inch pan (see note) with cooking spray and set aside.
For the bars, in a large bowl, cream together the butter, brown and granulated sugars, sour cream, egg, and vanilla until well-mixed, 1-2 minutes.
Blend in the bananas and mix.
Stir in the flour, baking soda and salt and mix for just a minute or two until combined.
Pour the batter evenly into the prepared pan and bake for 15-20 minutes until a toothpick inserted in the center comes out clean and the top springs back to the touch.
While the bars are baking, make the frosting by melting the butter in a saucepan or stainless steel (not nonstick) skillet over medium heat (here's a quick tutorial on browning butter). Bring the butter to a gentle simmer, turning the heat down if needed, until the solids lightly brown and the butter smells caramelly and fragrant. Immediately remove from the heat and add the powdered sugar, vanilla and milk, whisking until smooth and creamy. Add more milk if needed to achieve a thick but spreadable consistency.
Let the bars cool for 5-10 minutes and then dollop the frosting over the warm bars and spread in an even layer.
Cool the bars to room temperature. Cut into squares and serve. These keep well-covered for 1-2 days at room temp or refrigerated.
Notes
Doubling + Pan Size: this recipe doubles beautifully for a large, rimmed baking sheet (around 11X17-inches). However, if you want thicker layers (of both the bars and the frosting), when doubled, use a 15X10-inch pan (I don't have one so I always opt for the larger size). Same goes for the regular recipe - if you have an 11X7-inch pan, that will work, too, for slightly thicker layers. I happen to like the thinner layers myself, easier to justify a couple more nibbles.Frosting:I prefer the frosting with cream instead of milk because it adds a rich creaminess to the frosting that offsets the sweetness but obviously milk will work too. The frosting sets up a little after the bars cool which is why I could get away with stacking them for the photos but they do better in a single layer especially if it's warm when serving.